From Churchill and Orwell: The Fight for Freedom, by Thomas E. Ricks (Penguin, 2017), Kindle Loc. 1849-76:
The whole theory of fighter defence was created to avoid what they called “standing patrols.” If you were guarding the country by having aeroplanes up all the time, you ran out of engine hours and you were on the ground when the attack occurred. So the RAF developed a system of reporting incoming raids. First, he used radar to plot the aircraft as they were approaching Britain and then he used the Observer Corps to spot them when they’d crossed the coast. All the information was fed to a filter room and then to an operations room where you got a picture of the developing raids plotted on a table. That picture would be three or four minutes old but it was sufficiently up to date to get the fighters off when they were really needed.
Thus the characteristic image of the Battle of Britain that we have today is of young tousle-haired pilots lounging near their aircraft, not flying but ready to go aloft at a moment’s notice. In historical retrospect, the British air defense system was the equivalent of a human-powered computer, a remarkable real-time information-processing system that worked so well in conserving British aerial resources—aircraft, pilots, and staff attention—that it was one reason the Royal Air Force actually grew more powerful with the passage of time in 1940. A second reason was that British aircraft factories finally swung into high gear.
The third reason that the British prevailed in the Battle of Britain was German incompetence in waging an aerial offensive. Contrary to the Teutonic reputation for martial skill, the Luftwaffe’s approach was “astonishingly amateur,” concluded Bungay, amounting to “little more than flying over England, dropping some bombs on various things to annoy people, and shooting down any fighters which came up as a result.” It is no accident, Bungay adds, that the military service operating so incoherently was the only one of the German armed forces led by a Nazi politician, Goering, who before going into politics had been a pilot during World War I. Hitler supposedly liked to say that he had a conservative army, a reactionary navy, and a Nazi air force. That politicized air arm flew into English airspace unprepared for what it would encounter. Hans-Ekkehard Bob, who flew a Messerschmitt 109 fighter, recalled being surprised on a fogbound day: “I experienced a Spitfire formation all of a sudden coming up from behind, having a clear line of fire and I wondered how this was even possible. Having no visibility whatsoever, from above nor from below, how was it possible that an enemy formation was able to get into a firing position from behind?” The answer, of course, was the well-tuned British radar and early warning system.
The Germans in their days of pride also consistently overestimated the damage they were doing, believing in mid-August 1940 that the British had only 300 working fighters available. In fact, they had 1,438—which was twice as many as they had on hand just six weeks earlier. The kill ratio always favored the British, who lost a total of 1,547 aircraft while destroying 1,887 German ones. On top of that, because most of the aerial combat took place over England, British pilots could fly many missions in one day, with their aircraft reloaded with ammunition in under four minutes. And when they were shot down, they often could parachute to friendly soil and fly again, while parachuting Germans who survived became prisoners of war, and those who ditched in the frigid waters of the channel often were lost either to drowning or hypothermia. (For the same reasons, the RAF lost more bomber crew members during this period than it did fighter pilots—801 from Bomber Command versus 544 for Fighter Command.)